Neither soluable or insoluable fiber contributes to dietary carb uptake. The main difference is that soluable fiber, as the article said, feeds gut flora and absorbs water. You get to deduct both kinds of fiber from the total carbs.

Bob's Red Mill flaxmeal has a total carbs listing of 4 and a fiber listing of 4 so theoretically net carbs should be zero but this is likely to be a rounding error.

If you look at the calories from fat = ~52.5 and protein = 12 and subtract that from total calories which is 60, you see that there are 7.5 calories missing. Those are from the net carbs that are present which equals just a tad under 2 g carbs per 2 Tbls of flax meal. I'm guessing that some of that isn't even digested because it is all mixed in with the fiber and most likely isn't efficiently absorbed.